Stabilized aromatic amines



Patented Nov. 19, 1946 STABILIZED AROMATIO AMINES Ernest L. Walters, SanFrancisco, Calif., assignor to Shell Development Company, San Francisco,Calif., a corporation of Delaware No Drawing. Application September 15,1943, Serial No. 502,707

8 Claims. (01. 260-578) i This invention relates to gasolines havingimproved oxidation stability and knock rating.

A principal object is to provide motor fuel of greater stability anddecreased age deterioration.

Another purpose is to produce aviation gasolines which are both high inoctane rating and low in gum forming or precipitating tendencies. Otherobjectives will be apparent from the following description.

In my copending application Serial No. 441,876, filed May 5, 1942, Ishowed that 2,4-dimethyl-6- tertiary butyl phenol possesses unique andextraordinary inhibitor powers for tetra-alkyl lead fluid as well as foran initially stable gasoline (such as substantially saturate gasolines,for example aviation gasoline, as distinguished from unstable or crackedgasoline), which stable gasoline has been rendered unstable by theaddition of tetra-alkyl lead.

I have now found that aniline Or an alkyl aniline having not more than 6carbon atoms in the alkyl radicals, in a relatively small amount butsubstantially greater than that'of the 2,4- diniethyl-G-tertiary butylphenol unexpectedly accelerates or increases the inhibiting effect of ethe 2,4-dimethyl-6-tertiary butyl phenol in addition to materiallyraising the anti-knock rating. This is especially true in initiallystable leaded motor fuels such as aviation gasoline in which2,4-dimethyl-6-tertiary butyl phenol is used with particulareifectiveness as an anti-oxidant. However, this cumulative inhibitingefiect of anilines and 2,4-dimethyl-6-tertlary butyl phenol may also beobserved in normally unstable or cracked gasolines which may or may notcontain lead.

The apparent reason for this cumulative effect is that2,4-dimethyl-6-tertiary butyl phenol stabilizes the aromatic amines bythemselves. Therefore the same inhibitor can be used to stabilize theamines, not only when they are dissolved in gasoline in relatively lowconcentration, but also when they are in the substantially pure state,i. e. undiluted, or else are in the form of concentrates.

Moreover, the inhibitor will also stabilize amines having a greaternumber of carbon atoms than indicated above, i. e. greater than 12, aswell as polycyclic aromatic hydrocarbon amines, e. g. variousnaphthylamines, alkyl naphthylamines, aryl naphthylamines,anthracylamines and the like.

It is understood that the inhibitor must be well distributed throughoutthe substance to be protected. Thus, if the amine is a liquid undernormal conditions, the inhibitor should be a true or colloidal solution.If it is a solid, the inhibitor may be incorporated by first melting theamine, distributing the necessary amount of inhibitor as by dissolvingit, and then allowing the mixture to solidify; or else by merelyspraying the inhibitor or a solution thereof onto the solid amine.

The ability of 2,4-dimethyl-6-tertiary butyl phenol to inhibit thedeterioration of aromatic amines is very outstanding, in that it is theonly gasoline inhibitor found among a large number tested whicheffectively protects the amines themselves.

Among the many mono nuclear aromatic hydrocarbon amines useful forblending with gasolines, particular mention may be made of thefollowing: aniline, N-monoand dimethyl or higher alkyl anilines (whichmay also be substituted in the nucleus), mono-, di-, and trimethyl andhigher alkylated anilines (which may also be substituted on the N atom),toluidines, xylidines, cymidine, cumidine, pseudo cumidine, etc. as wellas suitable substituted derivatives. Obviously, mixtures of aromaticamines, as well as the individual amines may be thus employed. Likewise,aromatic-rich petroleum fractions may be nitrated and reduced to givemixtures such as described in U. S. Patents 1,844,362 and 2,252,- 099which may be blended in a motor fuel according to the present invention.These amines by themselves have little if any anti-oxidant eifect.

Amounts of mono nuclear aromatic amines in gasolines between about 25%and 3% are quite effective, although at times higher or lower quantitlesmay be employed. The upper limit is usually prescribed by maximumboiling range specifications of the gasolines. Since the aromatic aminesare relatively high boiling, they may raise the upper boiling range ofthe gasoline above permissible limits if used in excessive amounts. Onthe other hand, amounts of the amines below the lower limit indicatedgive, as a rule, insuflicient improvement to warrant their use. Acontent of about 1% has been found to be particularly advantageous.

An effective range for the 2,4-dimethyl-6-tertiary butyl phenol ingasoline is between about .0001 and .1%. The gasoline if desired maycontain up to about 6 c. c. of tetra alkyl lead per gallon.

In undiluted aromatic amines, the content of the 2,4-dimethyl-6-tertiarybutyl phenol may range from about .01 to .1%, preferably .1 to .5%.

A further advantage in the use of my combination of aromatic amine and2,4-dimethyl-6- tertiary butyl phenol in gasoline is that when Mostavailable commercial inhibitors failed to materially improve the colorstability, and on the rioration products proceeds slowly and a visibleprecipitate forms only after extended aging. This is in marked contrastto the action of most oxidation inhibitors whose eflectiveness isusually terminated quite suddenly at the end of their period ofstabilization with the rapid formation of degradation products in thegasoline and the consequent prompt termination of the usefulness of themotor fuel.

The invention may be further illustrated by reference to tests made withpure xylidine (5-amino- 1,3-dimethy1 benzene) in a 100 octane aviationgasoline composed of approximately 45% straight run gasoline, 45%alkylate and cyclopentane and containing 4 cc. of tetra ethyl lead fluidper gallon.

Stabilization of typical amines is shown by the following data. A liquidmixture of amino xylenes was examined for color at intervals, and thetime elapsed to allow the darkening from 2 to 6 A. S. T. M. color at 90F. in the presence of air was determined. The following results wereobtained:

Inhibitor Time No inhibitor About 1 week. .2% 2,4-dlmethyi-6-iertlarybutyl phenol 3 months.

contrary many reduced the time of darkening to about one day.

This is a continuation in part of my copenciing application, Serial No.478,290, filed March 6, 1943.

I claim as my invention:

1. An aromatic hydrocarbon amine of improved stability containing finelydistributed 2,4-dimethyl-fi-tertiary butyl phenol in amounts of .01 to1% calculated on the amine.

2. The composition of claim 1 wherein said amount is between .1 and .5%.

3. Normally liquid aromatic hydrocarbon amine of improved stabilitycontaining dissolved 2,4-dimethyl-6-tertiary butyl phenol in an amountof .01 to 1% calculated on the amine.

4. A mono nuclear aromatic hydrocarbon amine of improved stability inwhich the total number of carbon atoms in all alkyl radicals is lessthan '7, containing finely distributed 2,4-dimethyl-6-' tertiary butylphenol in amounts oi. .01 to 1% calculated on the amines.

5. A composition of improved stability comprising a mononuclear aromatichydrocarbon amine selected from the group consisting of aniline, N-alky]aniline, and nuclear alkyl-substituted aniline, and containing dissolved2,4-dimethylfi-tertiary butyl phenol in amounts of .01 to 1% calculatedon the aniline.

6. .Toluidine of improved stability containing dissolved2,4-dimethyl-6-tertiary butyl phenol in amounts of .01 to 1% calculatedon the toluidine.

'7. Xylidine of improved stability containing finely distributed2,4-dimethyl-6-tertiary butyl phenol in amounts of .01 to 1% calculatedon the xylidine.

8. Normally liquid xylidines of improved stability containing dissolved2,4-dimethyl-6-tertlary butyl phenol in amounts of .01 to 1% calculatedon the xylidine.

ERNEST L. WALTERS.

